Magnetic and thermodynamic properties of Sr_{2}LaFe_{3}O_{9}

Using a Dirac-Heisenberg Hamiltonian with biquadratic exchange interactions, we study the effect of iron disproportionation on the magnetic ordering, and describe the first-order magnetic transition occurring in the perovskite Sr_{2}LaFe_{3}O_{9}. Upon fitting the experimental data, we give an estimate of the exchange integrals for the antiferromagntic and ferromagnetic interactions, in agreement with previous works on kindered compounds. Spin-wave theory yields a magnon spectrum with a gapless antiferromagnetic mode together with two gapped ferromagnetic ones.Comment: 8 pages of RevTex, 5 figures (available upon request), submitted to J. Mag. Mag. Ma

Sparsity driven ultrasound imaging

An image formation framework for ultrasound imaging from synthetic transducer arrays based on sparsity-driven regularization functionals using single-frequency Fourier domain data is proposed. The framework involves the use of a physics-based forward model of the ultrasound observation process, the formulation of image formation as the solution of an associated optimization problem, and the solution of that problem through efficient numerical algorithms. The sparsity-driven, model-based approach estimates a complex-valued reflectivity field and preserves physical features in the scene while suppressing spurious artifacts. It also provides robust reconstructions in the case of sparse and reduced observation apertures. The effectiveness of the proposed imaging strategy is demonstrated using experimental data

Temperature-dependent soft x-ray photoemission and absorption studies of charge disproportionation in La1−x_{1-x}Srx_xFeO3_3

We have measured the temperature dependence of the photoemission and x-ray absorption spectra of La$_{1-x}$Sr$_x$FeO$_3$ (LSFO) epitaxial thin films with $x=0.67$, where charge disproportionation ($3{Fe}^{3.67+}\to 2{Fe}^{3+}+ {Fe}^{5+}$) resulting in long-range spin and charge ordering is known to occur below $T_{CD}=190$ K. With decreasing temperature we observed gradual changes of the spectra with spectral weight transfer over a wide energy range of $\sim 5$ eV. Above $T_{CD}$ the intensity at the Fermi level ($E_F$) was relatively high compared to that below $T_{CD}$ but still much lower than that in conventional metals. We also found a similar temperature dependence for $x=0.4$, and to a lesser extent for $x=0.2$. These observations suggest that a local charge disproportionation occurs not only in the $x=0.67$ sample below $T_{CD}$ but also over a wider temperature and composition range in LSFO. This implies that the tendency toward charge disproportionation may be the origin of the unusually wide insulating region of the LSFO phase diagram.Comment: 6 pages, 8 figure

Multi-Resolution Analysis and Fractional Quantum Hall Effect: an Equivalence Result

In this paper we prove that any multi-resolution analysis of \Lc^2(\R) produces, for some values of the filling factor, a single-electron wave function of the lowest Landau level (LLL) which, together with its (magnetic) translated, gives rise to an orthonormal set in the LLL. We also give the inverse construction. Moreover, we extend this procedure to the higher Landau levels and we discuss the analogies and the differences between this procedure and the one previously proposed by J.-P. Antoine and the author.Comment: Submitted to Journal Mathematical Physisc

Atmospheric Variability Of Methyl Chloride During the Last 300 Years From an Antarctic Ice Core and Firn Air

Measurements of methyl chloride (CH3Cl) in Antarctic polar ice and firn air are used to describe the variability of atmospheric CH3Cl during the past 300 years. Firn air results from South Pole and Siple Dome suggest that the atmospheric abundance of CH3Cl increased by about 10% in the 50 years prior to 1990. Ice core measurements from Siple Dome provide evidence for a cyclic natural variability on the order of 10%, with a period of about 110 years in phase with the 20th century rise inferred from firn air. Thus, the CH3Cl increase measured in firn air may largely be a result of natural processes, which may continue to affect the atmospheric CH3Cl burden during the 21st century

The Cosmic Infrared Background Experiment (CIBER): Instrumentation and First Results

Ultraviolet emission from the first generation of stars in the Universe ionized the intergalactic medium in a process which was completed by z similar to 6; the wavelength of these photons has been redshifted by (1 + z) into the near infrared today and can be measured using instruments situated above the Earth's atmosphere. First flying in February 2009, the Cosmic Infrared Background ExpeRiment (CIBER) comprises four instruments housed in a single reusable sounding rocket borne payload. CIBER will measure spatial anisotropies in the extragalactic IR background caused by cosmological structure from the epoch of reionization using two broadband imaging instruments, make a detailed characterization of the spectral shape of the IR background using a low resolution spectrometer, and measure the absolute brightness of the Zodiacal light foreground with a high resolution spectrometer in each of our six science fields. The scientific motivation for CIBER and details of its first and second flight instrumentation will be discussed. First flight results on the color of the zodiacal light around 1 mu m and plans for the future will also be presented

Observations of the Near-infrared Spectrum of the Zodiacal Light with CIBER

Interplanetary dust (IPD) scatters solar radiation which results in the zodiacal light that dominates the celestial diffuse brightness at optical and near-infrared wavelengths. Both asteroid collisions and cometary ejections produce the IPD, but the relative contribution from these two sources is still unknown. The low resolution spectrometer (LRS) onboard the Cosmic Infrared Background ExpeRiment (CIBER) observed the astrophysical sky spectrum between 0.75 and 2.1 μm over a wide range of ecliptic latitude. The resulting zodiacal light spectrum is redder than the solar spectrum, and shows a broad absorption feature, previously unreported, at approximately 0.9 μm, suggesting the existence of silicates in the IPD material. The spectral shape of the zodiacal light is isotropic at all ecliptic latitudes within the measurement error. The zodiacal light spectrum, including the extended wavelength range to 2.5 μm using Infrared Telescope in Space (IRTS) data, is qualitatively similar to the reflectance of S-type asteroids. This result can be explained by the proximity of S-type asteroidal dust to Earth's orbit, and the relatively high albedo of asteroidal dust compared with cometary dust

Parental bonding and identity style as correlates of self-esteem among adult adoptees and nonadoptees

Adult adoptees (n equals 100) and non-adoptees (n equals 100) were compared with regard to selfesteem, identity processing style, and parental bonding. While some differences were found with regard to self-esteem, maternal care, and maternal overprotection, these differences were qualified by reunion status such that only reunited adoptees differed significantly from nonadoptees. Moreover, hierarchical regression analyses indicated that parental bonding and identity processing style were more important than adoptive status per se in predicting self esteem. Implications for practitioners who work with adoptees are discussed

The Cosmic Infrared Background Experiment (CIBER): A Sounding Rocket Payload to Study the Near Infrared Extragalactic Background Light

The Cosmic Infrared Background Experiment (CIBER) is a suite of four instruments designed to study the near infrared (IR) background light from above the Earth's atmosphere. The instrument package comprises two imaging telescopes designed to characterize spatial anisotropy in the extragalactic IR background caused by cosmological structure during the epoch of reionization, a low resolution spectrometer to measure the absolute spectrum of the extragalactic IR background, and a narrow band spectrometer optimized to measure the absolute brightness of the Zodiacal light foreground. In this paper we describe the design and characterization of the CIBER payload. The detailed mechanical, cryogenic, and electrical design of the system are presented, including all system components common to the four instruments. We present the methods and equipment used to characterize the instruments before and after flight, and give a detailed description of CIBER's flight profile and configurations. CIBER is designed to be recoverable and has flown twice, with modifications to the payload having been informed by analysis of the first flight data. All four instruments performed to specifications during the second flight, and the scientific data from this flight are currently being analyzed

Determining the Weak Phase γ\gamma From Charged BB Decays

A quadrangle relation is shown to be satisfied by the amplitudes for $B^+ \to \pi^0 K^+,~\pi^+ K^0,~\eta K^+$, and $\eta' K^+$. By comparison with the corresponding relation satisfied by $B^-$ decay amplitudes, it is shown that the relative phases of all the amplitudes can be determined up to discrete ambiguities. Making use of an SU(3) relation between amplitudes contributing to the above decays and those contributing to $B^{\pm} \to \pi^{\pm} \pi^0$, it is then shown that one can determine the weak phase $\gamma \equiv {\rm Arg} (V_{ub}^* V_{cb}/V_{us}^* V_{cs})$, where $V$ is the Cabibbo-Kobayashi-Maskawa matrix describing the charge-changing weak interactions between the quarks $(u,c,t)$ and $(d,s,b)$.Comment: 16 pages, latex, 7 uuencoded figure